The present invention relates to a vehicle occupant protection system for improving the vehicle crash safety.
In recent years, with the aim of improving the safety of vehicle occupants at the time of a vehicle crash, various vehicle body structures have been proposed in which the deformation mode of the part of a vehicle body other than the passenger compartment is appropriately controlled in such a manner that the deceleration of the passenger compartment of the vehicle is reduced, and the deformation would not reach the passenger compartment (see Japanese patent laid-open publication No. 07-101354 and others).
One of the important factors which determine the seriousness of the injury of a vehicle occupant is the maximum value of the acceleration (or deceleration) of the vehicle occupant. Therefore, to minimize the injury of the vehicle occupant, the deceleration (in case of a frontal crash) should be reduced. The deceleration of the vehicle occupant is produced by the force applied from a restraint system such as a seat belt. Because a seat belt functions as a spring, the maximum value of the deceleration of the vehicle occupant occurs when the elongation of the seat belt is maximized as the vehicle occupant moves forward under the inertia force. The maximum value of the deceleration of the vehicle occupant increases in relation with the increase in the forward travel of the vehicle occupant under the inertia force, and may even exceed the average deceleration of the vehicle body.
When the relationship between the vehicle deceleration and the occupant deceleration is represented by input and output to and from a system consisting of a spring (the restraint system) and mass (the mass of the vehicle occupant), one can appreciate that the maximum elongation of the spring and the time at which this occurs are dictated by the waveform (time history) of the vehicle body deceleration. Therefore, to minimize the vehicle occupant deceleration at the time of a vehicle crash, it is necessary not only to reduce the average deceleration of the vehicle body but also to reduce the overshoot due to the presence of the spring (seat belt), by adjusting the waveform of the vehicle body deceleration.
In most of the conventional vehicle body structures, a crushable zone formed at a front portion of the vehicle body between a crash reaction generating member (such as side beams) and other components is allowed to deform so as to absorb the impact energy, and the waveform of the vehicle body deceleration is adjusted by changing the reaction property through appropriate selection of dimensions of various parts.
In any case, there is no doubt that the waveform of the vehicle body deceleration is an important factor in reducing the injury of the vehicle occupant. FIG. 9 shows a waveform of the deceleration of the seat belt that would favorably control the vehicle occupant deceleration according to the foregoing considerations. As indicated by the solid line, a deceleration which is greater than the average deceleration of the vehicle body is initially produced for a prescribed (short) time period, and then, a deceleration in the opposite direction is produced for another prescribed (short) time period. Thereafter, the seat is allowed to decelerate at the average deceleration. According to simulation runs conducted by the inventors, it was found that such a waveform of the vehicle seat deceleration can reduce the vehicle occupant deceleration more favorably than applying a constant deceleration (square wave) if the distance for the vehicle to decelerate (or the dynamic stroke) is the same.
According to a conventional vehicle body structure, a relatively weaker part of the crushable zone tends to deform initially, and it is followed by the deformation of a relatively stronger part of the crushable zone. Therefore, the waveform of the crash reaction or the vehicle body deceleration demonstrates a relatively low initial level which is followed by a period of a high level, and this is not desirable in reducing the deceleration of the vehicle occupant. To eliminate this problem, it has been proposed to achieve a constant reaction by controlled collapsing of the side beams, and to maintain a stable reaction by providing a plurality of partition walls in the side beams (Japanese patent laid open publication No. 07-101354).
However, such proposals were only capable of allowing the vehicle to decelerate at a constant rate (square wave), and were not suited for achieving a desirable deceleration waveform as shown in FIG. 9. To reduce the deceleration of the vehicle occupant from that of the conventional arrangement, it is necessary to achieve the waveform of the vehicle seat deceleration as shown in FIG. 9.
Proposals have been made in copending U.S. Pat. application Ser. Nos. 09/377,366 and 09/376,888 both filed on Aug. 18, 1999, to impart a relative deceleration and acceleration to the vehicle seat or the member carrying the vehicle seat with respect to the main part of the vehicle body so that the vehicle occupant may experience a deceleration from an early stage of a vehicle crash, and the maximum vehicle occupant deceleration may be reduced by distributing the inertia force acting on the vehicle occupant over a longer period of time. In such previously proposed arrangements, the seat belt was incorporated in the seat as opposed to the convention seat belt which is attached to the vehicle body except for the seat belt buckle which is normally attached to the seat. There are additional copending U.S. patent applications of later filing dates which also relate to similar subject matters. The contents of these applications are hereby incorporated in this application by reference.
However, as it is preferable to minimize the weight of the vehicle body and to use a standard seat belt having a retractor attached to the vehicle body, a further improvement of the arrangement is desired.
In view of such a recognition by the inventors, a primary object of the present invention is to provide a vehicle occupant protection system which can favorably reduce the vehicle occupant deceleration at the time of a vehicle crash by using a highly simple structure.
A second object of the present invention is to provide a vehicle occupant protection system which is adapted to the standard design of the seat belt and the vehicle body.
A third object of the present invention is to provide a vehicle occupant protection system which would not substantially increase the weight of the vehicle body.
According to the present invention, such objects can be accomplished by providing an automotive vehicle occupant protection system, comprising: a moveable part of a vehicle body including a vehicle seat and moveable in a fore-and-aft direction with respect to a vehicle body; a power source which is adapted to apply a rearward force to the moveable part in an early phase of a vehicle crash, and a forward force to the moveable part immediately following the early phase; a seat belt for the seat having a first anchor point which is attached to the moveable part, and a second anchor point which is attached to a fixed part of the vehicle body.
Thus, as the moveable part moves rearward as a result of a vehicle crash, the seat belt is pulled rearward, and performs the function to apply a deceleration to the vehicle occupant in an early phase of the vehicle crash. This is followed by a slight slackening of the seat belt as the moveable part is subjected to a forward force. Thus, an early application of a forward deceleration followed by the application of an acceleration which tends to mitigate the unacceptable sharp rise of the deceleration of the vehicle occupant achieves a desirable time history of deceleration for the vehicle occupant, and minimizes the injury to the vehicle occupant for a given stroke of deformation of the vehicle body.
The power source may consist of an active power actuator such as a high pressure gas generating device for applying a rearward force and/or forward force to the moveable part. Alternatively, the power source may comprise an impact transmitting member such as a G control member which forms a part of the moveable part, and is adapted to apply a rearward force to the moveable part as the impact transmitting member receives an impact from a vehicle crash. Also, the power source may comprise a stopper member which is interposed between the moveable part and a fixed part of the vehicle body, the stopper being adapted to collide with the moveable part as the moveable part moves rearward with respect to the vehicle body under the rearward force.
Typically, the first anchor point consists of a seat belt buckle, and the second anchor point consists of a shoulder anchor of the seat belt. The anchor points may include a third anchor point which may be attached either to the moveable part or to a fixed part of the vehicle body.